1. Field of the Invention
The present invention relates to a piezoelectric element having an electromechanical conversion function. In particular, the present invention relates to a piezoelectric element that makes it possible to obtain an excellent piezoelectric characteristic when used in an ink-jet recording head, a method for the manufacture thereof, and an ink-jet recording head and a printer using such piezoelectric elements.
2. Description of the Related Art
Ink-jet recording heads use piezoelectric elements as driving mechanism for ink ejection in printers. The piezoelectric elements usually comprise a piezoelectric thin film and a top electrode and a bottom electrode disposed so as to sandwich the film.
Piezoelectric elements with improved characteristics have been developed by regulating the crystal structure of a thin film composed of lead zirconium titanate (PZT) or forming Ti nuclei on the bottom electrode. For example, Japanese Patent Application Laid-open No. H10-81016 disclosed a PZT thin film provided with a rhombohedral crystal structure and the prescribed orientation degree. Furthermore, Japanese Patent Application Laid-open No. H8-335676 disclosed a piezoelectric element in which a titanium nucleus was formed on an Ir bottom electrode.
However, the problem associated with the conventional piezoelectric elements was that piezoelectric films with prescribed orientation degree were difficult to obtain with good stability and reproducibility. Such piezoelectric elements could not provide stable and good piezoelectric characteristics and accounted for insufficient printing performance of ink-jet recording heads or printers.
The prescribed orientation degree of piezoelectric film was especially difficult to obtain with good stability and reproducibility when a bottom electrode formed on a diaphragm was patterned to the prescribed shape and then a piezoelectric film was formed on the bottom electrode. Another problem was that the thickness of the bottom electrode became non-uniform and the crystals of the piezoelectric film became discontinuous in the vicinity of the patterning boundary of bottom electrode.